1. Technical Field
The present invention relates to an optical position detection device which optically detects the position of a target object, an optical position detection system, and a display system with an input function.
2. Related Art
An optical position detection device has been proposed to detect a target object. In such a device, a plurality of point light source sections and a plurality of light receiving sections are provided at positions separated from each other. When detection light is emitted from each of the light source sections toward a target object through a light transmissive member, detection light reflected from the target object is transmitted through the light transmissive member and is then detected by the light receiving sections (refer to JP-T-2003-534554). The optical position detection device detects the position of the target object using a condition in which the received light intensity in a light receiving section changes according to a distance from a light source to the light receiving section via the target object.
In addition, an optical position detection device has also been proposed in which the light intensity distribution, in which the intensity changes in the in-plane direction of a light guide plate, is formed at one surface side of the light guide plate by emitting detection light, which is emitted from each of a plurality of point light source sections, through the light guide plate and detection light reflected from the target object located in a space, in which the light intensity distribution is formed, is detected by a light receiving section (refer to JP-A-2010-127671 and JP-A-2009-295318). In this optical position detection device, the light intensity changes with the position of the target object. Accordingly, the optical position detection device detects the position of the target object in the in-plane direction of the light guide plate using a condition in which the amount of light reflected from the target object changes with the position of the target object.
In the optical position detection devices disclosed in JP-T-2003-534554, JP-A-2010-127671, and JP-A-2009-295318, however, there is a problem in that the range where the position of the target object can be detected is narrow. That is, in the optical position detection device disclosed in JP-T-2003-534554, the detection light emission angle range is narrow since detection light emitted from a point light source is used. For this reason, the range where the position of the target object can be detected is narrow. In addition, in the optical position detection devices disclosed in JP-A-2010-127671 and JP-A-2009-295318, it is necessary to increase the size of the light guide plate to extend a range where the position of the target object can be detected. However, if the large light guide plate is used, large attenuation occurs when detection light propagates through the light guide plate. For this reason, since it is difficult to form a predetermined light intensity distribution with a sufficient intensity level over a wide range, the range where the position of the target object can be detected is narrow.
Moreover, to detect the three-dimensional position of the target object in the optical position detection device disclosed in JP-T-2003-534554, it is necessary to dispose a plurality of point light source sections in a three-dimensional manner. In this case, however, since the emission angle range of the detection light emitted from the light source sections is narrow, the range where the position of the target object can be detected becomes extremely narrow. In addition, to detect the three-dimensional position of the target object in the optical position detection devices disclosed in JP-A-2010-127671 and JP-A-2009-295318, it is necessary to form an intensity distribution in which the intensity changes in a direction normal to the light guide plate. It is difficult to form such an intensity distribution with a large light guide plate. Therefore, the range where the position of the target object can be detected is extremely narrow.